1. Field of the Invention
This invention relates to a bitumen composition. More particularly this invention relates to a composition comprising bitumen and a polymeric modifier.
2. Prior Art
Bitumen compositions, particularly asphalt compositions, comprising one or more polymeric modifiers are, of course, well known in the prior art. In general, the addition of a polymeric modifier to a bitumen composition, particularly an asphalt composition, will improve one or more of the bitumen properties such as penetration, softening point, toughness, tenacity, heat resistance and the like such as taught in Japanese Patent No. Sho 58(1983)-47057. Suitable polymeric additives include: symmetric radical block copolymers comprising arms having diene polymer blocks and vinyl aromatic polymer blocks such as taught in U.S. Pat. No. 4,217,259; block copolymers of a monoalkenyl aromatic hydrocarbon monomer and a conjugated diolefin such as taught in U.S. Pat. No. 4,585,816 and the patents therein cited; olefin homopolymers and copolymers, particularly 1-butene homopolymers and copolymers, as taught in U.S. Pat. No. 3,915,914 and the patents therein cited; and isoolefin homopolymers, particularly polyisobutylene, such as taught in U.S. Pat. No. 3,615,803.
It is, of course, well known in the prior art to use asphalt compositions comprising polymeric modifiers in the preparation of road surfaces. In general, such road surfaces provide satisfactory service, at least on low traffic roads, for extending periods of time. Failure of such services is, however, inevitable, failures generally occur through bleeding, fatting up, cracking and chip loss. As is well known, the time until failure varies with several factors such as the amount and weight of traffic and various weather factors such as temperature and rainfall. Unfortunately, failure frequently occurs at shorter time intervals than desired. Such failures are due primarily to the poor toughness and tenacity of the asphalt composition. This is particularly true on heavily traveled roadways. The need, then, for an improved asphalt composition having improved toughness and tenacity thereby extending the time period between failures is believed to be readily apparent.